The discussion below is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.
An aspect of the present invention pertains to a process for manufacturing lactic acid in high purity in an economical manner.
Lactic acid is often manufactured via fermentation of carbohydrates by micro-organisms. A common feature to all fermentation processes is the need to neutralise the acids excreted by the micro-organisms. A drop in pH below a critical value, depending on the micro-organism used in the process, could damage the micro-organism's metabolic process and bring the fermentation process to a stop. Therefore, it is common practice to add a base in the fermentation media in order to control the pH. This results in the lactic acid produced being present in the fermentation media in the form of a lactate salt.
Despite the longstanding practice to produce lactic acid via fermentation, one of the challenges in the manufacture of lactic acid is still to obtain the acid in a relatively pure form while at the same time carrying out the process in an economical manner on a scale which is commercially attractive.
Electrodialysis is one of the purification processes that may be used in the production of lactic acid via fermentation. Water-splitting electrodialysis in particular allows the direct conversion of the lactate salt into lactic acid and base. In this type of electrodialysis bipolar membranes are generally used to split water into H+ and OH− respectively, which combine with the anion and cation of the lactate salt respectively, resulting in the production of separate solutions of lactic acid and base.
The use of water-splitting electrodialysis on aqueous media provided by fermentation, in particular for manufacturing organic acids, has been limited by the necessity to remove fermentation-derived products from the feed (e.g. sugar, protein and amino acids). Such fermentation derived matter negatively interferes with the water-splitting electrodialysis process by, for instance, fouling of the ion-permeable membranes and increasing the power consumption.
There is still need for a process for manufacturing lactic acid which provides lactic acid in high purity and which can be performed in an economical manner with low power consumption, without producing substantial amounts of non-reusable components (i.e. waste by-products) and without substantial yield loss.